| mutation | 1. A change in form, quality or some other characteristic. 2. <genetics> A permanent transmissible change in the genetic material, usually in a single gene. Also, an individual exhibiting such a change. Also called (in classical genetics) a sport. Origin: L. Mutatio from mutare = to change (18 Nov 1997) |
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| mutation rate | The frequency with which a particular mutation appears in a population or the frequency with which any mutation appears in the whole genome of a population. Normally the context makes the precise use clear. See: fluctuation analysis. (18 Nov 1997) |
| private mutation | A rare mutation found usually only in a single family or a small population. It is like a privately printed book. (12 Dec 1998) |
| homeotic mutation | <embryology, genetics> A mutation that causes an organism to develop a homologous body part or structure in place of the part or structure that should normally be there (for example, developing a hand in place of a foot). (09 Oct 1997) |
| silent mutation | Mutations that have no effect on phenotype because they do not affect the activity of the product of the gene, usually because of codon ambiguity. (18 Nov 1997) |
| site specific mutation | An alteration of the structure of a gene at a specific sequence, usually referring to experimentally produced changes in gene sequence. (05 Mar 2000) |
| somatic mutation | Mutation that occurs in the somatic tissues of an organism and that will not, therefore, be heritable, since it is not present in the germ line. Some neoplasia is due to somatic mutation, a more conspicuous example is the reversion of some branches of variegated shrubs to the wild type (completely green) phenotype. Somatic mutation is probably also important in generating diversity in V gene regions of immunoglobulins. (18 Nov 1997) |
| somatic mutation theory of cancer | That cancer is caused by a mutation or mutations in the body cells (as opposed to germ cells), especially nonlethal mutations associated with increased proliferation of the mutant cells. (05 Mar 2000) |
| spontaneous mutation | A mutation which occurs by itself without first being affected by a mutagen, for example during the process of DNA replication. Spontaneous mutations arise at a remarkably constant rate. The rate that spontaneous mutations arise has been used as an evolutionary clock to estimate how closely related two (or more) separate species are to each other. (09 Oct 1997) |
| natural mutation | A mutation which occurs by itself without first being affected by a mutagen, for example during the process of DNA replication. Spontaneous mutations arise at a remarkably constant rate. The rate that spontaneous mutations arise has been used as an evolutionary clock to estimate how closely related two (or more) separate species are to each other. (09 Oct 1997) |
| neutral mutation | A mutation that has no selective advantage or disadvantage. Considerable controversy surrounds the question of whether such mutations can exist. (18 Nov 1997) |
| new mutation | Redundant term for a heritable trait present in the offspring but in neither parent, i.e., not a pre-existing mutant form inherited. (05 Mar 2000) |
| substitution mutation | A mutation caused by a nucleotide base being replaced by a different one. (09 Oct 1997) |
| nonsense mutation | <molecular biology> A mutation that causes a polypeptide chain to be ended prematurely. (13 Nov 1997) |
| null mutation | Change in a gene that leads to nothing, for example to no enzyme or to a nonfunctioning enzyme. (12 Dec 1998) |